Method and apparatus for transporting and storing frozen comestibles



Feb. 26, 1952 L. wEs'rLlNG 2,586,893

' METHOD AND APARATUS FOR TRANSPORTING AND STORING FROZEN COMESTIBLESFiled Feb. 23, 1949 2 SHEETS-SHEET l i; y: l n 'I Ql: l l 'fi l I n n n:P

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IN VEN TOR.

LESTER L. WEST/ uva ATTORNEY Feb. 26, 1952 L. L. wEsTLlNG METHOD ANDAPPARATUS FOR TRANSPORTING AND STORING FROZEN COMESTIBLES 2Sl-IEETS-SI-IEET 2 Filed Feb. 25, 1949 INVENTOR.

LESTER L. WESTL//VG ATTORNE Y Patented Feb. 26, 1952 ori-ica METHOD ANDAPPARATUS FOR TRANS- PORTING AND STORING FROZEN C- MESTIBLES Lester L.Westling, Oakland, Calif. Application February 2s, 1949, serial No.77,734

(c1. ca -24) Claims.

This invention relates to refrigeration compartment and method ofrefrigeration and has particular adaptation to the refrigeration ofcomestibles which are quick-frozen and are mostadvantageously'maintained at or below plus 5 F. The invention isparticularly adaptable for use in connection with railway refrigeratorcars and the like which utilize a refrigerant consisting of a mixture ofice and chemical salt. 'I'he inven tion will be described withparticular reference to its use in a railway 'refrigerator car, it beingunderstood that the invention may be applied to other installations.

One obstacle to continued expansion of the quick-frozen fruit,vegetable, meat, nsh and poultry industry is the difficulty oftransportation over long distances with existing equipment. The presentinvention is designed to decrease the expense of transportation of suchgoods, in-l crease the range over which they may be transported andimprove the properties of the foods transported, particularly withreference to weight, palatableness, appearance and nutritional value.Such goods are best preserved at a constant temperature of plus 5 F. orlower and with the moisture content of the surrounding atmosphere at ornear saturation so that moisture is not removed from the food andtransmitted to the refrigerating medium. If the temperature fluctuates,various elements in the food which, by reason of the quick-freezingprocess, exist in the form of small crystals, may melt and uponrefreezing reform into larger crystals with consequent breaking down ofthe cell structure of the food and damage to the appearance,palataoleness, and nutritional value thereof. Normal railroadtransportation occasions cyclic rises and falls inV temperature byreason of melting of the ice and re-icing of the cars and for otherreasons such as weather changes, changes in altitude and differences innight and day conditions. Such cyclic changes in temperature have aparticularly disadvantageous effect on frozen foods in that they promotethe gradual building up of larger ice crystals.

Evaporation of moisture from the food diminishes the weight and alsodamages the comestibles both from the standpoint of appearance,palatableness and nutritional value. Existing methods of transporting orstoring quickfrozen foods for long periods tend to cause considerableevaporation of moisture from the foods, as well as raising of thetemperature above the desirable maximum and further result in cyclicelevations of temperature above the desired maximum. 'I'he almostuniversal means of refrigerating railway cars is by the deposit of saltand ice mixtures in bunkers at either end of the cars. A common mixtureemploys 30% sodium chloride and the remainder ice and results in asummer minimum car temperature of approximately 12 F. Air is circulatedthrough the bunkers filled with salt and ice mixture and into thecentral compartment of the car either by means or fans or by naturaldraft. The railway industry has a considerable investment in car icingfa.- cilities, and it is one of the features of the present invention tomake use of such facilities and not to require the investment of capitalin new or different facilities.

.The use of a 30% mixture of salt and ice results in a minimumrefrigerating temperature of about 12 F. which is higher than thedesired maximum temperature for maintaining quickfrozen foods. Thusexisting facilities tend to bring into equilibrium the temperature ofthe quick-frozen food and the salt and ice mixture, and it is necessaryinitially to lower the temperature of the food considerably below 0 F.so that its temperature during transit will not rise too high, and eventhis expedient is successful only for relatively short periods of timebefore equilibrium is reached at a higher temperature than is desired.The necessity of re-icing refrigerating cars under present conditions tokeep the temperature down results in an elapsed time of five to twelvedays for a transcontinental trip, and during such period of time thetemperature of the frozen foods is raised above the desired maximum withconsequent deleterious effect. Among the objects of the presentinvention are the provision of facilities for increasing the range overwhich frozen foods may be transported at suitable temperatures andimprovement of the quality of food from the standpoint of weight,moisture content, appearance, palatableness and nutritional value.

It is another principal object of the present invention to provide arefrigerating compartment which will maintain a satisfactory environmentfor the transportation or storage of such goods as frozen foods andpreserve the moisture content of the goods and maintain the temperaturethereof at a substantially uniform level lower than that now possible bythe use of conventional salt and ice mixture refrigeration methods.

Another principal object of the present invenl tion is the attainment ofthe foregoing objects by means of the novel construction of arefrigeration compartment in which there are two layers 3 of insulatingmaterial interposed between the outside atmosphere and the compartmentin which the goods are stored. with espace between the two layers ofinsulation through which a refrigerating medium. such as chilled air,may be circulated. Thus heat leaking from the outside is largely removedby the chilled air which circulates through the space between the layersat about 12 F. Since the space between the layers of insulation ismaintained at a temperature greatly less than that of the atmosphereoutside the refrigerating car, the temperature dinerential between theinterior of the car and the space between the layers of insulation isrelatively small, and the leakage between such space and the interior ofthe car is consequently small.

Another object of the invention is to eliminate the intimate contact ofthe circulating refrigerating medium, such as chilled air, with thegoods being refrigerated, and hence to eliminate the removal of moisturefrom the goods.

A further object of the invention is to absorb or cushion majoratmospheric temperature changes so that the temperature of the cargo isaffected only slightly, if at all. The temperature fluctuation islargely absorbed by the air jacket between the layers of insulation andthe proportionate difference between the temperature of the jacket andthat of the cargo is less than that between the atmosphere and thecargo.

Another object of the invention is to decrease the time required tochill a car in preparation for loading.

Still another object of the invention is the provision of means whichmay be used to convert the refrigerating car to a refrigeration systemsimilar to that used in conventional cars at the present time, but withcertain advantageous features which increase the insulation of theinterior from the atmosphere.

Further objects of the present invention will become apparent uponreading the following specification and referring to the accompanyingdrawings in which similar characters of reference representcorresponding parts in each of the several views.

In the drawings:

Fig. l is a longitudinal vertical section through a car.

Fig. 2 is a transverse vertical section of a half of a car.

Fig. 3 is a fragmentary horizontal sectional view through a side walltaken along the line 3-3 of Fig. 2.

Fig. 4 is a schematic view illustrating the drop in temperature from theoutside atmosphere assumed to be at 92 F. to an interior compartment atF. wherein the space between two layers of insulation is cooled by airat 12 F.

Fig. 5 is a view similar to Fig. 4 wherein the space between the twolayers of insulation is closed off and constitutes a dead air space.

As has been stated, the present invention is described by reference toits installation in a railway car, but it will be understood that theinvention is capable of use in other media.

a refrigerating medium. such as a mixture of ice and salt i8, which isdeposited in the bunkers through a plurality of doors I3 in the roof ofthe car communicating with the bunkers and is supported upon horizontalbunker grates 20 which permit circulation of air through the bunker andrefrigerant. It will be understood that various means of driving thefans could be employed when the car is stationary, as at a loadingplatform or when the invention is put to use other than in connectionwith rolling stock. The use of a mixture of 30% salt and 70% ice resultsin a plenum temperature of about 12 F., and consequently, as the air isforced or through natural means circulates through the mixture, thetemperature of the plenum air is reduced to, at or about 12 F. Inconventional refrigeration, this chilled air is caused to circulatethrough the contents of the car, and thus removes part of the heatleaking into the car from the atmosphere and also tends to bring thetemperature of the contents into equilibrium with the temperature of thebunkers. Such temperature is too high for frozen foods for the reasonswhich have been explained, and the circulation of chilled air throughquick-frozen foods tends to remove at least part of the moisture thereofand to raise the temperature thereof with the deleterious effectshereinbefore mentioned.

Where very cold outside temperatures are experienced it may be necessaryto heat the cars by circulation of warm air through the space betweenlayers of insulation, heating frequently being accomplished bycombustion. In such instances, the gases resulting from combustionand/or the lowhumidity air do not reach the cargo but circulate in thespace between layers of insulation.

In the present invention the chilled air passing through the bunkers I1may be channeled so that it does not come into contact willi the foodbeing transported, and hence it cannot remove moisture from the food. Inaccordance with the present invention the food is stored inside acentral compartment 2i to which access is afforded by side doors (notshown) suitably insulated.

4 The goods may be stacked upon a floor rack or In the accompanyingdrawings there is shown l platform 22 spaced above the floor of the car.The compartment is insulated by two separate layers of insulationmaterial 23 and 24 with a space 26 therebetween through which circulateschilled air from the bunkers I1 in an uninterrupted circuit around theroof, sides and floor of the car. The interior compartment 2i isprovided with a lining 21 of plywood, fibre board, metal or othersuitable substance on the sides 28, ends 29, roof 30 and oor 3| toreduce Wear and so that the interior may easily be cleaned whennecessary. The lining 21 is attached by adhesive or other suitablefastening means to interior insulation 23 which surrounds thecompartment 2| and lining 21 on all sides4 thereof. Spaced from theinterior insulation 23 is an exterior insulation 24 which may beattached by adhesive or other suitable fastening to the roof 32, floor33, sides 34 and ends 35 of the car. The insulation may be of anysuitable type but preferably has structural and compressive strength asWell as high insulating efliciency.

Interposed between the interior and exterior insulations along the sidesof the car are spacing means 38 attached to said respective insulationsby adhesive or other fastening means and separating the two layers ofinsulation 23 and 24 from each other and establishing the space 26therethe sides.

between. The spacers 38 shown in the preferred embodiment particularlywith reference to Fig. 3 are corrugated so as to aiord a plurality ofvertical channels 39. These unobstructed channels provide a flue eilectto enhance air circulation through space 26 when fans I6 are notoperating. In conventional refrigerator cars, circulaton of air throughthe cargo space by natural draft is obstructed by the cargo itself,particularly when the fans are stopped as, for example, during re-icing.The channels 39 augment natural draft circulation and hence tend to keepa constant cargo tempera-ture even when the fans I6 are stopped.

The spaces between the t'wo layers of insulation at the top and bottomof the car are somewhat greater in cross-sectional area than the spacesbetween the two layers of insulation at Further, the roof 32 of afreight car generally slopes downward from a central crown so that thespace between the two layers of insulation is greater along the centerthan near the sides of the car. Similarly, the fioor 33 may be slopeddownward at the center to provide a greater space at the center of thebottom of the car than along the sides. The enlarged spaces ports 53 andup through end bunker I1.

constitute plenums 40 and 4| for movement of air longitudinally of thecar. For the purpose of supporting the insulation and load along the topand bottom of the car, there are a plurality of transverse webs 42 and'43 at the top and bottom, respectively, and to permit free circulationof air through the plenums 4| and 40 across which these webs extend,holes 44 are spaced in the webs to provide longitudinal communicationfrom one end bunker I1 to the other so that the air may circulate freelylongitudinally of the car at the top and bottom plenums and be channeleddownwardly or upwardly in the plurality of channels 39 formed by thespacers 38.

In Fig. 3 there is shown corrugated material interposed between theinner layer 23 and outer layer 24 of insulation, said corrugationsconsisting of risers 46 which hold the two layers apart a fixeddistance, the risers being associated with parallel faces 41 and 48transverse to risers 46 which are alternately on one side or the otherof the two layers of insulating material. Optionally, sheets 49extending across the faces4 41 and 48 are joined to spacers 38 bywelding or other suitable manner and aiiixed to insulation 23 and 24 byadhesive or other means. It will be understood that the construction ofthe spacers 38 is subject to wide modication. It will be observed,however, that the spacers shown in the preferred embodiment haveconsiderable structural strength and tend to support the weight of theinsulation and contents of the cargo. The channels provide convenientmeans for uniform distribution of chilled air longitudinally of the car.

Positioned adjacent the top and bottom of each of the bunkers |1 areinsulated dampers 5|) and 5I, respectively, hingedly connected to theinterior insulation at hinge pivot 52. The dampers,

are adjustable in three positions. In one position of adjustment eachdamper affords communication between the bunker I1 and the plenums 40and 4| by opening ports 53 communicating between the bunkers and plenumsand closing ports 54 communicating between the bunkers I1 and interiorcompartment 2|. A second position of adjustment closes the ports 53communicating from the bunker l1 to the plenums 40 and 4| and opens theports 54 communicating between the bunkers I1 and the interiorcompartment 2| of space to 0 the car. A third or intermediate adjustmentis provided in which there is communication from the bunkers I1 throughboth ports 53 and 54 into both the compartment 2| and plenums 40 and 42.In the rst position of adjustment of the dampers the car is availablefor use in connection with transportation of quickfrozen foods. In thesecond position of adjustment the car is adaptable for use similar toconventional refrigerating cars but with improved effect. In the thirdposition of adjustment the car is adapted for rapid pre-cooling. Adescription of the use of the car in each of the three positions ofadjustment follows.

In the rst position cf adjustment of dampers 50 and 5|, as isl shown inFig. 1, air is circulated by the fans I6 through the bunker |1 and iscooled by the salt and ice mixture I8 to a temperature about 12 F. Theports 53 being open, the chilled air passes through said ports andthrough the longitudinal upper plenum 4| and branches out and travelsdown through the channels 39 in the spacers 38 between the layers ofinsulation 23 and 24 of the side walls, thence down to the lower plenum40 and through the By such air circulation the temperature of the space26 between the two layers of insulation tends to reach a level of about12 F. It will be understood that a reverse flow may be employed in whichcase the air is drawn through the bunker |1 by fan I6 thence throughlower plenum 40, up through channels 39 and back to the bunker throughupper plenum 4|.

The advantages of the invention may be illustrated by example. Assumingthat the temperature of the outside atmosphere is 92 F. and that thequick-frozen foods inside the compartment are at 0 F., as is shown bythe temperature gradient diagram Fig. 4, the temperature drops from 92F. on the exterior of the car through the outer insulation 24 to thetemperature of 12 F. in the space 26 between the two layers ofinsulation 23 and 24 and then drops from 12 F. in said F. in theinterior compartment through the interior insulation 23. Hence the majorportion of the heat which leaks into the car from the outside atmosphereis intercepted and removed in the space 26 between .the insulationlayers, and, therefore. the difference in temperature between the space7.6 and the interior compartment 2| is relatively small as compared withthe difference in temperature between the interior compartment 2| andexternal atmosphere. Accordingly, the leakage of heat into the interiorcompartment is relatively slight, for the heat leakage is a directfunction of the temperature differential between the two sides of thelayer of insulation. The reduction in heat leakage into the interiorcompartment prolongs the period of time during which frozen food ismaintained at low temperature. Furthermore, since the air does notcirculate through the interior compartment it does not remove moisturefrom the cargo.

The heat gained or lost through a thickness of insulation may beexpressed by the formula:

lation used expressed in B. t. u./hour/inch/ thickness/deg. F. Diff.

7 t=thickness of insulation in inches Tir-temperature on one side ofinsulation Tz=temperature on opposite side of insulation Referring nowto Fig. 4 and computing H through insulation 24 and assuming A=100 sq.ft.

t=3 in.

K=.28 for corkboard insulation Computing H through insulation 23 andassumins A=100 sq. ft. t=3 in. T1=12 F. Tz= F. K=.28

Thus only 112 B. t. u. of heat per hour is absorbed by the cargo,whereas 747 B. t. u. is absorbed by the chilled air and goes to melt theice in bunkers The value of the present invention may be seen bycomputing the thickness of solid insulation required to produce acorresponding low heat absorption. Assume H=l12 B. t. u. per hour A= 100sq. ft.

T2=0 F. (assuming a refrigerant were used to provide such a temperature,i. e., some refrigerant other than salt and ice) Then tzmoxasxigr-o t=23in.

Thus by the present invention a saving of 17 inches in thickness ofinsulation results with consequent reduction in cost, weight and time ofprecooling for like conditions.

The second position of adjustment of the dampers 50 and 5| providescommunication from the bunkers I1 to the interior compartment 2|,through ports 54. and thus permits circulation of air around the cargomuch as in conventional refrigerator cars. In lthis position ofadjustment the cars may be used normally for transportation of foods ata higher temperature than in the first position of adjustment. It willbe observed that the space 26 between the layers of insulation is closedoff by the dampers 50, and hence there is a dead air space between thetwo layers of insulation 23 and 24 which enhances the insulation effectbetween the interior compartment 2| and the external atmosphere. Asshown in Fig. 5 assuming a temperature of 92 F. in the exterioratmosphere, it will be seen that the dead air space 26 between the twolayers of insulation 23 and 24 enhances the insulation effect andresults in a lower interior temperature in compartment 2|l salt-to-iceratios or at reduced expenditure oi the same.

Referring to Fig. 5, assuming insulation 23 and 24 to be each threeinches in thickness and the dead air space 26 to be one-and-one-halfinches and K for a dead air space to be 1.2, thus it will be observedthat considerably less heat is transferred to the interior compartmentthan would be the case were a solid wall of insulation six inches thickto be used.

The third position of adjustment-namely, when both the ports 53 and 54are openprovides for rapid pre-cooling of the cars. It will beunderstood that when refrigeration cars are not in use and stand infreight yards the temperature of the interior compartment 2| and thetemperature of the air entrained in the insulation layers 23 and 24rises to about the temperature of the surrounding atmosphere or evenhigher by reason of solar radiation. In pre-cooling the cars, it isnecessary to withdraw heat not only from the interior compartment 2| butalso from the insulation layers 23 and 24. In the third position ofadjustment of the dampers 50, the area of insulation subjected tochilled air is approximately trebled. Thus the air in the interiorcompartment 2| is refrigerated and also the layers of the insulation aresubjected to refrigeration on three separate surfaces-namely, th'esuri'ace of inner layer 23 which communicates with the interiorcompartment, the surface of inner layer 23 which communicates with space26, and the surface of exterior layer 24 which communicates with space26. Therefore,

. the time consumed in lowering the temperature of the insulation ismaterially decreased because a greater surface area is subjected torefrigeration. Although this position of adjustment is advantageous forrapid pre-cooling, it is also useful in certain situations where atemperature slightly below 12 F. is desired. It s possible by adjustmentof dampers 50 and 5| to balance circulation through the space 26 andcompartment 2| in any desired ratio.

It is further apparent that the dampers at one end bunker may be in oneposition of adjustment and those at the other end at a differentposition. Thus flexibility is imparted to the system, which is desirableparticularly if the two bunkers are at different temperatures by reasonof different salt-and-ice ratios, and a compounded eifect is desired forcompartment 2|.

It will be understood that metallic surfaces, such as the spacers 38 andcar exteriors 32 to 35, inclusive, are preferably fashioned of brightmetal or are painted or enameled white or a bright color so as to reduceheat absorption. Other enclosed metal should, preferably, be corrosionresistant.

The present invention is, therefore, particularly useful in connectionwith transportation of quick-frozen foods for relatively long distanceswhere the refrigerant most economically employed is one such as amixture of salt and ice, which produces a refrigerating temperaturehigher than the optimum for the goods beingl to the temperaturedifferential between the two sides of the insulation layers, the heatleaking into the cargo is thereby reduced. This permits transportationof cargoes over longer distances because the quick-frozen food is notelevated in temperature as rapidly as would be the case if solidinsulation were employed. It is also significant that the chilled airdoes not circulate through the cargo for otherwise, as in conventionalinstallations, the air would remove moisture from the food, therebyreducing weight, damaging the appearance of the food, and decreasingnutritional value.

By making the dampers 50- and 5I adjustable, as has been indicated, thepresent invention may be used in two alternative ways-namely, as a meansof quickly pre-cooling a car which has been standing in a yard with theresult that the insulation has absorbed considerable heat, and as aconventional refrigerator car but withl improvement in insulatingquantities by reason of the dead air space provided when the ports 53are closed.

Although the invention has been described as applied to a railwayrefrigerator car, it will be understood that with suitable modificationsit may be used in other installations, either stationary ortransportable. It will, further, be understood that the invention isadaptable to use with refrigerants other than salt and ice, and in factif weather conditions necessitate, heated air may be circulated in thespace between the layers of insulation.

Although I have described my invention in some detail by way ofillustration for purposes of clarity of understanding, it is understoodthat certain changes and modications may be made trolling circulationthrough said ports, and means for circulating air through said bunkers.

2. A refrigerating compartment comprising a cargo-accommodating walledenclosure, a. ilrst layer of insulation about said enclosure, a secondlayer of insulation about said first layer, spacing means for spacingsaid layers apart, a bunker for.

a refrigerating medium, a rst port communieating between said bunkerandsaid enclosure, a second port communicating between said bunker andsaid spacing means, damping means vcontrolling circulation through saidports, and means for circulating air through said bunkers, said dampingmeans being adjustable to at least three positions including, a firstposition establishing circulation between said bunker and said spacingmeans, a second position establishing circulation between said bunkerand said enclosure,- and a third position establishing circulationbetween said bunker and both said spacing means and said enclosure.

3. A refrigerating compartment vcomprising a cargo-accommodating walledenclosure, at least one wall thereof having a rst layer of insulation, asecond layer of insulation outside said first layer, and spacing meansfor spacing said layers apart, said spacing means including, Webs in thespace between said layers at the top and bottom of said enclosureextending transversely to the direction of movement of air through thespace between said layers, said webs being apertured to permit movementof air and risers disposed between said layers at the sides of saidenclosure to support structurally said layers and defining a pluralityof vertical channels, the spaces at the top and bottom of said enclosureforming plenums for circulation of refrigerated air in a circuit from asource of refrigerated air out through the plenum in the space at thetop of said enclosure, thence down through said vertical channels andback through the plenum at the space at the bottom of said enclosure tosaid source, and means for circulating air through said spacing means.

4. A refrigerating compartmentas defined in claim 1 and wherein one ofsaid layers at the top of the compartment is positioned at an angle withrespect to the other ofsaid layers so that the distance between saidlayers is greater along the longitudinal center of the top of said`compartment than along the sides thereof thereby forming a top plenumfor circulation of air along the top of said spacing means, and one ofsaid layers at the bottom of the compartment is positioned at an anglewith respect to the other of said layers so that the. distance betweensaid layers is greater along the longitudinal center of the top of saidcompartment than along the sides thereof thereby forming a bottom plenumfor circulation of air along the bottom of said spacing means.

5. A refrigerator car comprising a bunker, a lading chamber, a firstlayer of insulation enclosing said chamber, a second layer of insulationsurrounding said rst layer, spacing means separating said lavers, a rstport communicating between said bunker and said spacing means, a secondport communicatingr between said bunker and said chamber, a dampercontrolling circulation through said ports, and a fan for circulatingrair through said bunker and selectively upon adiustment of said damperthrough land through a space between plural layers of insulationenclosing and defining said compartment, and maintaining said cargobelow the temperature of said cooled air by circulating cooled air onlythrough the space between said plural layers of insulation.

. 7. A method of maintaining pre-chilled cargo at or near itspre-chilled temperature comprising, depositing an ice and salt mixturein a bunker. loading said compartment with a pre-chilled cargo below thetemperature of said bunker-chilled air.

tively narrow streams outside the sides of said compartment and avertical stretch through said bunker, said path of travel beinginsulated from said compartment thereby substantially maintaining thetemperature of said pre-chilled cargo below the temperature of saidbunker-cooled air.

8. A refrigerating compartment comprising a cargo-accommodating walledenclosure, a iirst layer of insulation about said enclosure, a secondlayer of insulation about said ilrst layer, spacing means for spacingsaid layers apart, a source of refrigerated air, a rst portcommunicating between said source and said enclosure, a second portcommunicating between said source and said spacing means, and dampingmeans controlling circulation through said ports.

9. A refrigerating compartment comprising a cargo-accommodating walledenclosure, a first layer oi insulation about the bottom, top, sides andan end of said enclosure, a second layer of insulation about said ilrstlayer, spacing means for spacing said layers apart and establishingspaces between layers of insulation at the top, sides, an end and thebottom of said compartment, said spacing means in the sides of saidcompartment being formed to establish a plurality of vertical channelscommunicating between the spaces at the top and bottom of saidcompartment, the space at the end of said compartment communicating withthe spaces at the top and bottom of said compartment, and meansestablishing a ilow of refrigerated air in a circuit through said spaceswherein portions o1' said circuit extend longitudinally of saidcompartment l l2 along the top thereof, vertically along the sides ofsaid compartment, longitudinally along the bottom of said compartmentand vertically at an end of said compartment.

10. A method of maintaining pre-chilled cargo at or near its pre-chilledtemperature comprising. depositing an ice and salt mixture in a bunker.loading a compartment with a pre-chilled cargo below the temperature ofsaid bunker-chilled air, and then circulating bunker-chilled air througha space between plural layers of insulation surrounding and definingsaid compartment, said circulation following a path of travel from saidbunker longitudinally above said compartment above the top thereof, thenvertically downward in a plurality of relatively narrow streams outsidethe sides of said compartment, and then longitudinally below saidcompartment back to said bunker, said path of travel being insulatedfrom said compartment thereby substantially maintaining the temperatureof said pre-chilled cargo below the temperature of said bunkercooledair.

LESTER L. WES'I'LING.

REFERENCES CITED 'I'he following references are of record in the file ofthis patent:

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